The present invention relates to a structure and a method for connecting bus bars in an electric junction box for electrically connecting an electric component block such as a fuse block to a circuit board assembly including wiring circuit boards, bus bar circuit boards and so on, by way of bus bars, by welding.
FIGS. 6 and 7 show one example of a conventional connecting structure of bus bars in an electric junction box, which is disclosed in Japanese Patent Publication No. 2001-309526A (cf., Page 3 and FIGS. 1 to 5).
This electric junction box comprises: an assembly 51 of a plurality of bus bar circuit boards which are stacked one on another, a relay block 54 which is connected by welding to terminal portions 53 of bus bars 52 (see FIG. 7) of the circuit board assembly 51; a fuse block 55 which is disposed on the circuit board assembly; and a cover 56 (see FIG. 7) made of synthetic resin for covering a sub assembly of these elements.
Each of the bus bars 52 is formed by stamping an conductive sheet metal into a desired circuit shape, and by bending a desired end portion of the bus bar 52 at a right angle or by extending it straightly to form a terminal portion 53. The terminal portion 53 projects from one side edge of the circuit board assembly 51, and is connected by welding to a terminal portion 57 at one end of bus bar 66 of the relay block 54. Both the terminal portions 53 and 57 are clamped between a pair of electrodes of a resistance welding machine (not shown), and electrically heated to be welded. The relay block 54 is juxtaposed with the circuit board assembly 51.
A terminal portion (not shown) at the other end of the bus bar 66 of the relay block 54 is connected to a relay connecting terminal (not shown) in a relay mounting part 65. Terminal portions 58 projected from edges of the circuit board assembly 51 constitute a fuse connecting part in cooperation with terminal portions 59 of the fuse block 55, for example. A fuse (not shown) having a pair of terminals is connected to the fuse connecting part. The bus bars 60 of the fuse block 55 are connected to vertical terminal portions 62 of the bus bars 61 of the circuit board assembly 51, for example.
Other terminal portions 63 vertically uprighted from the circuit board assembly 51 are contained in a housing part 64 of the cover 56 (see FIG. 7) to constitute a connector or the like. An exterior wire harness (a power source circuit or an auxiliary equipment circuit) is connected to the connector. In this manner, the power source in the exterior, the bus bars, the relays, the fuses and an auxiliary equipment are mutually connected.
However, in the above configuration, when the terminal portions 57 of the relay block 54 are connected to the terminal portions 53 of the circuit board assembly 51, they are positioned and welded by abutting the terminal portions 53, 57 in an L-shape against each other in a direction of their thickness. For this reason, there has been such an anxiety that the terminal portions 53, 57 may be excessively pushed and deformed, resulting in variations in welding strength, and reliability of the electrical connection is liable to be deteriorated.
There has been a further anxiety that when the terminal portions 53, 57 are abutted against each other, the bus bars 66 of the relay block may be pushed in a longitudinal direction and may give bad influences to the terminals in the relay mounting part 65 to deform them. Moreover, since relative position of the circuit board assembly 51 with respect to the relay block 54 is determined by the connecting position between the terminal portions 53 and 57, the positions of the circuit board assembly 51 and the relay block 54 to be fixed to the cover (not shown) may vary due to variations of the connecting position, which leads to an anxiety that an assembling work cannot be conducted smoothly. Further, because it has been difficult to position the terminal portions 57 of the relay block 54 with respect to the terminal portions 53 of the circuit board assembly 51, there has been an anxiety that a lot of trouble and many positioning tools may be required, and connecting workability may be deteriorated.
It is therefore an object of the invention to provide a structure and a method for connecting bus bars, in which it is possible to reliably perform connections between the bus bars of a circuit board assembly and the bus bars of an electric component block provided with electric components such as relays, fuses.
It is also an object of the invention to provide a structure and a method for connecting bus bars, in which, in which it is possible to smoothly and reliably assemble the electric component block to the circuit board assembly with good workability, without being affected by variations or so in connecting positions between terminal portions of the respective bus bars.
In order to achieve the above objects, according to the invention, there is provided a connection structure in an electric junction box, comprising:
a first assembly, comprising:
a board member, for wiring an electric wire thereon; and
a first bus bar, electrically connected to the electric wire, and including a first tab-shaped terminal having a first dimension in a first direction and a second dimension smaller than the first dimension in a second direction perpendicular to the first direction; and
a second assembly, joined to the first assembly in the first direction, the second assembly comprising:
a mount section, in which an electric component is mounted; and
a second bus bar, electrically connected to the electric component, and including a second tab-shaped terminal having a third dimension in the first direction and a fourth dimension smaller than the third dimension in the second direction, wherein:
the first terminal and the second terminal are arranged so as to be overlapped in the second direction to be welded to each other, after the second assembly is joined to the first assembly, and arranged such that a relative position between the first terminal and the second terminal is gradually changed in the first direction during the joining operation of the first assembly and the second assembly.
In such a configuration, both the first and second terminals will not be affected by a pressure in the second (thickness) direction and bending deformation of the terminals will be prevented. Moreover, because the direction of joining the first and second assemblies is same as the first (widthwise) direction of the terminals, the second assembly will be smoothly joined to the first assembly without being affected by connection between the terminals (that is, the relative position in the joining direction). Therefore, for example, a terminal in the first assembly to be connected to the electric component can be perfectly placed at a predetermined position in the second assembly.
It is preferable that: the first terminal is provided at a side end portion of the first assembly in the second direction, and extending in a third direction orthogonal to the first direction and the second direction; and the second terminal is provided at a side end portion of the second assembly in the second direction, and extending in the third direction.
In such a configuration, it is possible to obtain enough space to weld the terminals extended in the third direction, while reducing the space required for the terminals in the second direction.
Here, it is further preferable that a top end of the first terminal is situated upper than a top face of the first assembly.
In such a configuration, the workability of the welding operation can be further enhanced.
It is also preferable that: the second bus bar includes a joint portion continued from the second terminal and extending in the second direction; and the joint portion is fitted into the mount section in the first direction to receive the electric component.
In such a configuration, even when the terminals are brought into contact with each other in the second direction and a repulsion force is generated therebetween, such a repulsion force will not serve as a force for removing the second bus bar from the second assembly. Therefore, the inadvertent removal of the second bus bar can be avoided.
It is also preferable that: the first bus bar includes a third terminal extending in the first direction; and the third terminal is placed in the mount section to receive the electric component when the second assembly is joined to the first assembly.
In such a configuration, since the direction of entering the third terminal into the mount section is the same as the joining direction of the assemblies, even if the terminals are brought into contact with each other in the second direction and a repulsion force is generated therebetween, such a repulsion force will not affect the joining operation.
It is also preferable that the connecting structure further comprises a positioning member for determining a relative position between the first assembly and the second assembly.
In such a configuration, the joining operation of the assemblies can be performed smoothly and reliably.
According to the invention, there is also provided a method of providing a connection structure in an electric junction box, comprising steps of:
providing a first assembly, comprising:
a board member, for wiring an electric wire thereon; and
a first bus bar, electrically connected to the electric wire, and including a first tab-shaped terminal having a first dimension in a first direction and a second dimension smaller than the first dimension in a second direction perpendicular to the first direction; and
providing a second assembly, comprising:
a mount section, in which an electric component is mounted; and
a second bus bar, electrically connected to the electric component, and including a second tab-shaped terminal having a third dimension in the first direction and a fourth dimension smaller than the third dimension in the second direction;
joining the second assembly to the first assembly in the first direction while a relative position between the first terminal and the second terminal is gradually changed in the first direction; and
welding the first terminal and the second terminal which are overlapped in the second direction, after the second assembly is joined to the first assembly.
It is preferable that: the first bus bar includes a third terminal extending in the first direction; and the second bus bar includes a joint portion continued from the second terminal and extending in the second direction. The method further comprises steps of: fitting the joint portion into the mount section in the first direction, before the second assembly is joined to the first assembly; and placing the third terminal in the mount section to receive the electric component when the second assembly is joined to the first assembly.